001/*
002 * Portions of this software was developed by employees of the National Institute
003 * of Standards and Technology (NIST), an agency of the Federal Government and is
004 * being made available as a public service. Pursuant to title 17 United States
005 * Code Section 105, works of NIST employees are not subject to copyright
006 * protection in the United States. This software may be subject to foreign
007 * copyright. Permission in the United States and in foreign countries, to the
008 * extent that NIST may hold copyright, to use, copy, modify, create derivative
009 * works, and distribute this software and its documentation without fee is hereby
010 * granted on a non-exclusive basis, provided that this notice and disclaimer
011 * of warranty appears in all copies.
012 *
013 * THE SOFTWARE IS PROVIDED 'AS IS' WITHOUT ANY WARRANTY OF ANY KIND, EITHER
014 * EXPRESSED, IMPLIED, OR STATUTORY, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY
015 * THAT THE SOFTWARE WILL CONFORM TO SPECIFICATIONS, ANY IMPLIED WARRANTIES OF
016 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE, AND FREEDOM FROM
017 * INFRINGEMENT, AND ANY WARRANTY THAT THE DOCUMENTATION WILL CONFORM TO THE
018 * SOFTWARE, OR ANY WARRANTY THAT THE SOFTWARE WILL BE ERROR FREE.  IN NO EVENT
019 * SHALL NIST BE LIABLE FOR ANY DAMAGES, INCLUDING, BUT NOT LIMITED TO, DIRECT,
020 * INDIRECT, SPECIAL OR CONSEQUENTIAL DAMAGES, ARISING OUT OF, RESULTING FROM,
021 * OR IN ANY WAY CONNECTED WITH THIS SOFTWARE, WHETHER OR NOT BASED UPON WARRANTY,
022 * CONTRACT, TORT, OR OTHERWISE, WHETHER OR NOT INJURY WAS SUSTAINED BY PERSONS OR
023 * PROPERTY OR OTHERWISE, AND WHETHER OR NOT LOSS WAS SUSTAINED FROM, OR AROSE OUT
024 * OF THE RESULTS OF, OR USE OF, THE SOFTWARE OR SERVICES PROVIDED HEREUNDER.
025 */
026
027package gov.nist.secauto.metaschema.core.util;
028
029import java.util.Objects;
030import java.util.stream.Stream;
031
032import edu.umd.cs.findbugs.annotations.NonNull;
033
034public final class ObjectUtils {
035  private ObjectUtils() {
036    // disable construction
037  }
038
039  /**
040   * Assert that the provided object is not {@code null}.
041   * <p>
042   * This method sets the expectation that the provided object is not {@code null}
043   * in cases where a non-null value is required.
044   *
045   * @param <T>
046   *          the object type
047   * @param obj
048   *          the object
049   * @return the object
050   */
051  @NonNull
052  public static <T> T notNull(T obj) {
053    assert obj != null;
054    return obj;
055  }
056
057  /**
058   * Require a non-null value.
059   *
060   * @param <T>
061   *          the type of the reference
062   * @param obj
063   *          the object reference to check for nullity
064   * @return {@code obj} if not {@code null}
065   * @throws NullPointerException
066   *           if {@code obj} is {@code null}
067   */
068  @NonNull
069  public static <T> T requireNonNull(T obj) {
070    if (obj == null) {
071      throw new NullPointerException(); // NOPMD
072    }
073    return obj;
074  }
075
076  /**
077   * Require a non-null value.
078   *
079   * @param <T>
080   *          the type of the reference
081   * @param obj
082   *          the object reference to check for nullity
083   * @param message
084   *          detail message to be used in the event that a {@code
085   *                NullPointerException} is thrown
086   * @return {@code obj} if not {@code null}
087   * @throws NullPointerException
088   *           if {@code obj} is {@code null}
089   */
090  @NonNull
091  public static <T> T requireNonNull(T obj, @NonNull String message) {
092    if (obj == null) {
093      throw new NullPointerException(message); // NOPMD
094    }
095    return obj;
096  }
097
098  /**
099   * A filter used to remove null items from a stream.
100   *
101   * @param <T>
102   *          the item type
103   * @param item
104   *          the item to filter
105   * @return the item as a steam or an empty stream if the item is {@code null}
106   */
107  @SuppressWarnings("null")
108  @NonNull
109  public static <T> Stream<T> filterNull(T item) {
110    return Objects.nonNull(item) ? Stream.of(item) : Stream.empty();
111  }
112
113  @SuppressWarnings("unchecked")
114  @NonNull
115  public static <T> T asType(@NonNull Object obj) {
116    return (T) obj;
117  }
118
119  @SuppressWarnings("unchecked")
120  public static <T> T asNullableType(Object obj) {
121    return (T) obj;
122  }
123}